Step actuator

ABSTRACT

Disclosed is a step actuator. The step actuator includes a housing; a stator installed in the housing; a rotor positioned radially inward from the stator, the rotor rotating and protruding from one side of the housing; a bearing installed at one side of the housing so as to be coupled with the rotor; a bearing cover coupled with one side of the housing to restrain movement of the bearing; a screw member coupled with the rotor to linearly move according to rotation of the rotor; and a mounting member coupled to the bearing cover to support the screw member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/056,455, filed Feb. 1, 2011, which is the U.S. National StageApplication of International Patent Application No. PCT/KR2008/006474,filed Nov. 3, 2008, which claims the benefit under 35 U.S.C. §119 ofKorean Patent Application No. 10-2008-0073770, filed on Jul. 28, 2008,all of which are herein incorporated by reference in their entirety.

TECHNICAL FIELD

The embodiment relates to a step actuator.

BACKGROUND ART

A step actuator includes a rotor and a stator. The step actuatorlinearly drives a shaft according to rotation of the rotor.

For instance, the step actuator is connected to a member, which drives areflector of a vehicle headlight system, in order to change thedirection of illumination. In addition, the step actuator converts therotational movement of the rotor into the linear movement, so the stepactuator can be applied to various electric and mechanical devicesrequiring the linear action.

DISCLOSURE Technical Problem

The embodiment provides a step actuator having a novel structure.

The embodiment provides a step actuator including a bearing cover forrestraining a bearing, and a mounting member coupled to the bearingcover to support a screw member.

The embodiment provides a step actuator including a bearing coverdetachably coupled to a mounting member.

The embodiment provides a step actuator including a bearing cover whichcan be easily coupled to a mounting member.

Technical Solution

A step actuator according to an embodiment includes a housing; a statorinstalled in the housing; a rotor positioned radially inward from thestator, the rotor rotating and protruding from one side of the housing;a bearing installed at one side of the housing so as to be coupled withthe rotor; a bearing cover coupled with one side of the housing torestrain movement of the bearing; a screw member coupled with the rotorto linearly move according to rotation of the rotor; and a mountingmember coupled to the bearing cover to support the screw member.

A step actuator according to an embodiment includes a housing; a statorinstalled in the housing; a rotor positioned radially inward from thestator, the rotor rotating and protruding from one side of the housing;a bearing installed at one side of the housing so as to be coupled withthe rotor; a bearing cover coupled with one side of the housing torestrain movement of the bearing; a screw member coupled with the rotorto linearly move in a first direction and a second direction, which isopposite to the first direction, according to rotation of the rotor; anda mounting member detachably coupled to the bearing cover to support thescrew member.

Advantages Effects

The embodiment can provide a step actuator having a novel structure.

The embodiment can provide a step actuator including a bearing cover forrestraining a bearing, and a mounting member coupled to the bearingcover to support a screw member.

The embodiment can provide a step actuator including a bearing coverdetachably coupled to a mounting member.

The embodiment can provide a step actuator including a bearing coverwhich can be easily coupled to a mounting member.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a step actuator according to anembodiment;

FIG. 2 is a sectional view showing a step actuator according to anembodiment;

FIGS. 3 and 4 are exploded perspective views showing a step actuatoraccording to an embodiment;

FIG. 5 is a perspective view showing a second housing that supports abearing from the first direction in a step actuator according to anembodiment;

FIGS. 6 and 7 are views showing bearing covers of a step actuatoraccording to another embodiment, respectively; and

FIGS. 8 to 12 are perspective views showing the structure and couplingrelationship between a bearing cover and a mounting member.

MODE FOR INVENTION

Hereinafter, a step actuator according to embodiments will be describedin detail with reference to the accompanying drawings.

In the drawings, the size and thickness of elements are exaggerated,omitted or simplified for the purpose of convenience or clarity ofexplanation. In addition, the elements may have sizes different fromthose shown in drawings, in practice.

FIG. 1 is a perspective view showing a step actuator according to anembodiment, FIG. 2 is a sectional view showing the step actuatoraccording to an embodiment, and FIGS. 3 and 4 are exploded perspectiveviews showing a step actuator according to an embodiment.

Referring to FIGS. 1 to 4, the step actuator according to an embodimentincludes a stator, a rotor that rotates while interacting with thestator, and a screw member 10 coupled to the rotor to linearlyreciprocate in the first and second directions according to forward andreverse rotation of the rotor.

The stator includes first and second bobbins 130 and 140, and first andsecond yokes 150 and 160 installed between first and second housings 110and 120.

The rotor includes a magnet 30 installed within the stator to rotatewhile interacting with the stator, and a nut member 20 coupled to themagnet 30. The screw member 10 and the nut member 20 are coupled to eachother in the form of a bolt-nut assembly. Thus, if the nut member 20rotates, the screw member 10 linearly moves.

In detail, the first and second bobbins 130 and 140 are installed in aspace formed between the first and second housing 110 and 120, and thefirst and second yokes 150 and 160 are disposed between the first andsecond bobbins 130 and 140.

In addition, the magnet 30, the nut member 20 and the screw member 10are disposed radially inward between the first and second bobbins 130and 140.

In addition, a bearing 40, a bearing cover 50, and a mounting member 60are installed at one side of the second housing 120.

In more detail, as the step actuator according to the embodimentoperates, the screw member 10 linearly reciprocates in the first andsecond directions, which are opposite to each other, along an axis ofthe screw member 10.

In addition, a first end of the screw member 10 is inserted into aprotrusion pipe 132 of the first bobbin 130 and a second end of thescrew member 10 passes through a protrusion 61 of the mounting member60. A joint 70 is coupled to the second end of the screw member 10.

A thread 11 is formed on an outer surface of the first end of the screwmember 10, and a stopper 12 is provided between the thread 11 and thesecond end of the screw member 10.

The thread 11 of the screw member 10 is coupled with a thread 21 formedon an inner surface of the nut member 20. Thus, the screw member 10moves in the first or second direction as the nut member 20 rotates.

The stopper 12 restrains the movement of the screw member 10 in thesecond direction. As the screw member 10 moves in the second direction,the stopper 12 is blocked by the protrusion 61 of the mounting member60, so that the screw member 10 cannot move in the second direction anymore. In addition, a blocking section 133 is provided at a first end ofthe protrusion pipe 132 of the first bobbin 130 in order to restrain themovement of the screw member 10 in the first direction.

The movement of the screw member 10 in the second direction can berestrained by minimizing a diameter of a perforation hole 62 of theprotrusion 61 of the mounting member 60 such that the thread 11 of thescrew member 10 cannot pass through the protrusion 61 of the mountingmember 60. In addition, the movement of the screw member 10 in the firstdirection can be restrained by minimizing a diameter of the first end ofthe protrusion pipe 132 such that the thread 11 of the screw member 10cannot pass through the protrusion pipe 132. Therefore, the blockingpart 133 and the stopper 12 can be selectively provided according to theapplication.

Meanwhile, as described above, the screw member 10 can linearly move inthe first or second direction by passing through the mounting member 60,but the rotation of the screw member 10 is restrained. That is, therotation of the screw member 10 is restrained by the protrusion 61 ofthe mounting member 60.

For instance, the second end of the screw member 10 is cut into a shapeof “D” and the perforation hole 62 of the mounting member 60 has a shapecorresponding to a sectional shape of the second end of the screw member10.

Since the screw member 10 cannot rotate, the screw member 10 linearlymoves in the first or second direction as the nut member 20 coupled withthe screw member 10 rotates.

The nut member 20 is inserted into the magnet 30 and a second end 22 ofthe nut member 20 protrudes in the second direction by passing throughthe magnet 30. A spline 23 is provided at an outer peripheral surface ofthe nut member 20. The spline 23 extends in the axial direction and iscoupled with a spline hole 31 formed in the magnet 30. Thus, the nutmember 20 rotates together with the magnet 30.

The second end 22 of the nut member 20 is coupled with an inner race ofthe bearing 40. Thus, the nut member 20 can freely rotate while beingsupported by the bearing 40.

In addition, the thread 21 formed in the inner surface of the nut member20 is coupled with the screw 11 formed on the outer surface of the screwmember 10. In addition, the nut member 20 is coupled with the protrusionpipe 132 of the first bobbin 130 and rotatably supported by theprotrusion pipe 132 of the first bobbin 130. That is, the inner surfaceof the nut member 20 makes contact with an outer surface of theprotrusion pipe 132.

The magnet 30 may include a permanent magnet having N and S poles whichare alternately arranged in the circumferential direction at the regularinterval. As mentioned above, since the nut member 20 is inserted intothe magnet 30, the nut member 20 rotates as the magnet 30 rotates.

Meanwhile, a second end 32 of the magnet 30 protrudes in the seconddirection so as to make contact with the inner race of the bearing 40.Thus, the magnet 30 can smoothly rotate without making contact with anouter race of the bearing 40 due to the second end 32 of the magnet 30.

The first bobbin 130 having a first coil 131 and the second bobbin 140having a second coil 141 are installed around the magnet 30. Inaddition, the first and second yokes 150 and 160 are arranged betweenthe first and second bobbins 130 and 140.

The first bobbin 130 includes a first coil winding section 134, aroundwhich the first coil 131 is wound, and a first terminal section 135electrically connected to the first coil 131. In addition, the secondbobbin 140 includes a second coil winding section 144, around which thesecond coil 141 is wound, and a second terminal section 145 electricallyconnected to the second coil 141.

As mentioned above, the first bobbin 130 has the protrusion pipe 132,into which the screw member 10 is inserted, and a slit 136, into which athird tooth 111 of the first housing 110 is inserted. The first bobbin130 faces the magnet 30 and the nut member 20. The first bobbin 130 hasa recess (not shown) to reduce friction among the first bobbin 130, themagnet 30 and the nut member 20 as the magnet 30 and the nut member 20move in the first or second direction.

The first yoke 150 includes a first body section 151 having a ringshape, a first tooth 152 protruding from an inner peripheral surface ofthe first body section 151 toward the first housing 110 so as to bedisposed between the first bobbin 130 and the magnet 30, and a firstgrounding terminal 153 for grounding the first body section 151. Inaddition, the second yoke 160 includes a second body section 161 havinga ring shape, a second tooth 162 protruding from an inner peripheralsurface of the second body section 161 toward the second housing 120 soas to be disposed between the second bobbin 140 and the magnet 30, and asecond grounding terminal 163 for grounding the second body section 161.

Meanwhile, the first housing 110 is provided with the third tooth 111protruding toward the second housing 120 so as to be disposed betweenthe first bobbin 130 and the magnet 30 by passing through the slit 136of the first bobbin 130. The third tooth 111 and the first tooth 152 arealternately arranged along a peripheral portion of the magnet 30.

The first housing 110 has a first rim section 112, which protrudesradially inward from the cylindrical body of the first housing 110, andthe third tooth 111 extends from the first rim section 112 in the seconddirection. A first opening 113 is defined by the first rim section 112and one side of the first bobbin 130 is inserted into the first opening113.

In addition, the second housing 120 has a fourth tooth 121 protrudingtoward the first housing 110 so as to be disposed between the secondbobbin 140 and the magnet 30. The fourth tooth 121 and the second tooth162 are alternately arranged along a peripheral portion of the magnet30.

The second housing 120 has a second rim section 122, which protrudesradially inward from the cylindrical body of the second housing 120, andthe fourth tooth 121 extends from the second rim section 122 in thefirst direction.

Meanwhile, a first cutting section 114 is formed in the first housing110 by cutting a predetermined portion of the first rim section 112, anda second cutting section 124 is formed in the second housing 120 bycutting a predetermined portion of the second rim section 122. The firstand second rim sections 114 and 124 form an opening. The first terminalsection 135 formed in the first bobbin 130, the first grounding terminal153 formed in the first yoke 150, a second grounding terminal 163 formedin the second yoke 160, and the second terminal section 145 formed inthe second bobbin 140 protrude outward through the opening defined bythe first and second rim sections 114 and 124.

The bearing 40 is installed at the second end of the second housing 120,and the bearing cover 50 is provided to support the bearing 40. That is,the bearing cover 50 is coupled to the second housing 120 to restrainthe bearing 40. For instance, the bearing cover 50 can be coupled to thesecond housing 120 through a spot welding or a laser welding.

As described above, the inner race of the bearing 40 makes contact withthe second end 22 of the nut member 20 and is supported by the secondend 22 of the nut member 20.

In addition, the movement of the bearing 40 in the first direction isrestrained by the second rim section 122 of the second housing 120, andthe movement of the bearing 40 in the second direction is restrained bythe bearing cover 50.

The diameter of a second opening 123 defined by the second rim section122 is larger than that of the magnet 30 and smaller than that of thebearing 40. Thus, friction may not occur between the magnet 30 and thesecond housing 120 and the movement of the bearing 40 in the firstdirection can be restrained.

FIG. 5 is a perspective view showing the second housing that supportsthe bearing from the first direction in the step actuator according toan embodiment.

Referring to FIG. 5, the nut member 20 is inserted into the magnet 30and is coupled with the inner race of the bearing 40.

The bearing cover 50 is coupled with the second housing 120 and themounting member 60 is coupled with the bearing cover 50 from the seconddirection.

The bearing 40 is installed between the bearing cover 50 and the secondhousing 120. The movement of the bearing 40 in the first direction isrestrained by the second rim section 122 of the second housing 120.

Referring to FIG. 5, the bearing 40 is partially exposed between thesecond rim section 122 and the magnet 30, and the remaining part of thebearing 40 is blocked by the second rim section 122 of the secondhousing 120 so that the movement of the bearing 40 in the firstdirection can be restrained.

FIGS. 6 and 7 are views showing bearing covers of the step actuatoraccording to another embodiment, respectively.

The bearing cover 50 is provided with a coupling section 54. Thecoupling section 54 is bent radially inward from the bearing cover 50 inorder to restrain the movement of the bearing 40 in the first direction.The coupling section 54 can be aligned on an outer race of the bearing40 through a caulking process.

Different from the step actuator shown in FIGS. 1 to 5, in which themovement of the bearing 40 in the first and second directions isrestrained by the second housing 120 and the bearing cover 50, themovement of the bearing 40 in the first and second directions isrestrained by the bearing cover 50 in the step actuator shown in FIGS. 6and 7.

If the bearing 40 is restrained by the second housing 120 and thebearing cover 50 in the step actuator according to the embodiment, themounting member 60 is not needed to restrain the bearing 40 in thespecific position. Thus, the mounting member 60 can be designed invarious shapes.

In addition, if the bearing 40 is restrained by the bearing cover 50 inthe step actuator according to the embodiment, the second housing 120and the mounting member 60 are not needed to restrain the bearing 40 inthe specific position. Thus, the second housing 120 and the mountingmember can be designed in various shapes.

FIGS. 8 to 12 are perspective views showing the structure and couplingrelationship between the bearing cover and the mounting member.

Similar to the bearing cover 50 shown in FIGS. 6 and 7, the bearingcover 50 shown in FIGS. 8 to 12 is provided with the coupling section54. The structure of the bearing cover 50 shown in FIGS. 8 to 12 isidentical to the structure of the bearing cover 50 shown in FIGS. 1 to5, except for the structure of the coupling section 54.

Referring to FIG. 8, the bearing cover 50 includes a coupling rim 51, acoupling pipe 52, a locking rim 53, a coupling section 54, a supportmember 55, a stopper protrusion 56, and a first contact member 57.

The coupling rim 51 has a ring shape with a predetermined width and iscoupled to the second rim section 122 of the second housing 120. Forinstance, the coupling rim 51 is coupled to the second rim section 122of the second housing 120 through a welding.

The coupling pipe 52 extends in the second direction from an innerperipheral surface of the coupling rim 51 such that an innercircumferential surface of the coupling pipe 52 makes contact with anouter race of the bearing 40.

The locking rim 53 protrudes radially inward from a second end of thecoupling pipe 52 to make contact with the outer race of the bearing 40.The locking rim 53 restrains the movement of the bearing 40 in thesecond direction.

As mentioned above, the coupling section 54 restrains the movement ofthe bearing 40 in the first direction. The coupling section 54 isvertically bent to support the bearing 40 and faces the locking rim 53while interposing the bearing 40 therebetween.

A plurality of support members 55 extend from an outer peripheralportion of the coupling rim 51 in the second direction while beingspaced apart from each other. A circular virtual line can be formed byconnecting the support members 55.

The stopper protrusion 56 extends radially outward from the supportmember 55. The stopper protrusion 56 includes first and second bendingmembers 56 a and 56 b which are arranged in the circumferentialdirection. The first and second bending members 56 a and 56 b aresupported on a locking member 64 and the locking protrusion 65 of themounting member 60 such that the mounting member 60 can be preventedfrom rotating in the circumferential direction when the mounting member60 is coupled with the bearing cover 50.

The first and second bending members 56 a and 56 b may enlarge thecontact area of the stopper protrusion 56, so that the stopperprotrusion 56 can be securely supported on the locking member 64 and thelocking protrusion 65.

The first contact member 57 extends radially outward from the second endof the support member 55 and makes contact with the second contactmember 67 of the mounting member 60 to prevent the mounting member 60from moving in the axial direction.

The mounting member 60 includes the protrusion 61, a receptacle pipe 63,the locking member 64, the locking protrusion 65, an extension rim 66and the second contact member 67.

The protrusion 61 and the receptacle pipe 63 forms a body of themounting member 60. The protrusion 61 supports the screw member 10 suchthat the screw member 10 can move in the first or second direction, andthe receptacle pipe 63 provides a space for installing the bearing 40and the bearing cover 50. The protrusion 61 protrudes from thereceptacle pipe 63 in the second direction.

The first end of the receptacle pipe 63 is inserted between the supportmember 55 of the bearing cover 50 and the coupling pipe 52. Thus, anouter peripheral portion of the first end of the receptacle pipe 63makes contact with an inner peripheral portion of the support member 55and an inner peripheral portion of the first end of the receptacle pipe63 makes contact with an outer peripheral portion of the coupling pipe52.

The extension rim 66 extends radially outward from an outer peripheralsurface of the receptacle pipe 63. The extension rim 66 has a ring shapeand faces the first stopper protrusion 56 and the first contact member57 of the bearing cover 50.

A plurality of locking members 64 extend from the outer peripheralportion of the extension rim 566 in the first direction while beingspaced apart from each other. An inner peripheral portion of the lockingmember 64 faces an outer peripheral portion of the coupling rim 51.

When the mounting member 60 rotates clockwise in a state in which thelocking member 64 is positioned between the support members 55 of thebearing cover 50, the first bending member 56 a makes contact with thecircumferential end of the locking member 64. Thus, the mounting member60 does not rotate clockwise any more.

The locking protrusion 65 has elasticity and is formed on the extensionrim 66 between the locking members 64. The locking protrusion 65 has ashape of a cantilever having a free end making contact with the secondbending member 56 b of the stopper protrusion 56.

That is, the locking protrusion 65 is positioned between adjacentsupport members 55, and then is locked with the second bending member 56b of the stopper protrusion 56 while moving along the stopper protrusion56 when the mounting member 60 rotates clockwise.

In order to allow the locking protrusion 65 to smoothly move along thestopper protrusion 56, the free end of the locking protrusion 65 isinclined.

The second contact member 67 extends radially inward from the first endof the locking member 64 while being spaced apart from the extension rim66 by a predetermined distance. The first contact member 57 is insertedbetween the second contact member 67 and the extension rim 66.

The mounting member 60 coupled to the bearing cover 50 from the seconddirection. Thus, when the mounting member 60 is coupled to the bearingcover 50, the second contact member 67, which is integrally formed withthe mounting member 60, is coupled to the first contact member 57, whichis integrally formed with the bearing cover 50, from the first directionso that the movement of the mounting member 60 can be restrained in thefirst and second directions.

In order to securely couple the bearing cover 60 to the mounting member60, an embossing 57 a is formed on the first contact member 57 thatmakes contact with the second contact member 67. The embossing 57 aadheres to the second contact member 67 when the locking member 64 andthe locking protrusion 67 are locked with the stopper protrusion 56 dueto the rotation of the mounting member 60, thereby supporting the secondcontact member 67 from the first direction.

Hereinafter, the method for coupling the mounting member 60 to thebearing cover 50 will be described with reference to FIGS. 9 to 12.

As shown in FIG. 9, the receptacle pipe 63 of the mounting member 60 isinserted between the support member 55 and the coupling pipe 52 of thebearing cover 50, and the locking member 64 and the locking protrusion65 of the mounting member 60 are positioned between the stopperprotrusions 56 of the bearing cover 50.

Differently from FIG. 10, the first contact member 57 of the bearingcover 50 does not overlap the second contact member 67 of the mountingmember 60 in the axial direction in FIG. 9.

Referring to FIGS. 9 and 10, if the mounting member 60 rotatesclockwise, as shown in FIG. 11, the locking member 64 makes contact withthe first bending member 56 a, and the locking protrusion 65 moves alongthe stopper protrusion 56 so that the free end of the locking protrusion65 makes contact with the second bending member 56 b. Thus, the mountingmember 60 is not rotated.

Similar to FIG. 12, the first contact member 57 of the bearing cover 50overlaps the second contact member 67 of the mounting member 60 in theaxial direction in FIG. 11. Thus, the first contact member 57 makescontact with the second contact member 67. Since the embossing 57 a isformed on the first contact member 57, the embossing 57 a adheres to thesecond contact member 67 while pushing the second contact member 67 inthe first direction. Therefore, the bearing cover 50 can be securelycoupled to the mounting member 60 without moving in the axial direction.

The mounting member 60 can be easily disassembled by rotating themounting member 60 counterclockwise after lifting up the free end of thelocking protrusion 165 in the second direction.

The step actuator according to the embodiment includes the bearing cover50, which restrains the position of the bearing 40 and supports themounting member 60, and the mounting member 60, which guides andsupports the linear movement of the screw member 10. Thus, the mountingmember 60 can be fabricated in various shapes and easily coupled withthe bearing cover 50.

In the step actuator described above, an electric field is generated aspower is applied to the first terminal section 135 and the secondterminal section 145, so that the magnet 30 rotates in the forwarddirection or the backward direction according to the electric field.

As the magnet 30 rotates, the nut member 20 coupled with the magnet 30also rotates, so that the screw member 10 having the thread 11 engagedwith the thread of the nut member 20 moves in the first direction or thesecond direction according to the rotation direction of the magnet 30.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure.

INDUSTRIAL APPLICABILITY

The step actuator according to the embodiment can convert the rotationalmovement into the linear movement, so the step actuator can be appliedto various electric and mechanical devices requiring the linear action.

The invention claimed is:
 1. A step actuator comprising: a housingstructure including a first housing and a second housing; a statorinstalled in the housing structure, wherein the stator includes a firstbobbin, a second bobbin, a first yoke having a first tooth, and a secondyoke having a second tooth installed between the first housing and thesecond housing; a rotor positioned radially inward from the stator, therotor rotating and protruding from one side of the housing structure; abearing installed at one side of the second housing; a bearing covercoupled with one side of the housing structure, wherein the bearingcover supports the bearing; a screw member coupled with the rotor; and amounting member coupled to the bearing cover, wherein the first housingincludes a third tooth protruding toward the second housing so as to bedisposed between the first bobbin and a magnet by passing through a slitof the first bobbin, wherein the second housing includes a fourth toothprotruding toward the first housing so as to be disposed between thesecond bobbin and the magnet; wherein the bearing cover includes acoupling rim having a ring shape and coupled to one side of the housingstructure, a coupling pipe extending from the coupling rim, and alocking rim protruding radially inward from an end of the coupling pipeto make contact with an outer race of the bearing; and wherein thebearing cover comprises a coupling section protruding radially inwardfrom the coupling rim to make contact with the outer race of thebearing.
 2. The step actuator as claimed in claim 1, wherein the screwmember linearly moves in a first direction and a second direction thatis opposite to the first direction.
 3. The step actuator as claimed inclaim 2, wherein movement of the bearing is restrained in the firstdirection by the one side of the housing structure.
 4. The step actuatoras claimed in claim 2, wherein movement of the bearing is restrained inthe second direction by the bearing cover.
 5. The step actuator asclaimed in claim 2, wherein the bearing cover makes contact with thebearing from the second direction and a radially outward direction. 6.The step actuator as claimed in claim 2, wherein the one side of thehousing structure is fixed to the bearing cover through a spot weldingor a laser welding.
 7. The step actuator as claimed in claim 1, whereinthe mounting member restrains rotation of the screw member.
 8. The stepactuator as claimed in claim 7, wherein one side of the screw member hasa D-shape section, and the mounting member is formed with a D-shapeperforation hole.
 9. The step actuator as claimed in claim 1, wherein aninner peripheral surface of the coupling pipe makes contact with theouter race of the bearing.
 10. The step actuator as claimed in claim 1,wherein the first bobbin comprises a first coil and a first terminalsection electrically connected to the first coil.
 11. The step actuatoras claimed in claim 10, wherein the first housing comprises a firstcutting section formed therein by cutting a predetermined portion of afirst rim section.
 12. The step actuator as claimed in claim 11, whereinthe first terminal section protrudes outward through an opening definedby the first rim section.
 13. The step actuator as claimed in claim 1,wherein the second bobbin comprises a second coil and a second terminalsection electrically connected to the second coil.
 14. A step actuatorcomprising: a housing; a stator installed in the housing; a rotorpositioned radially inward from the stator, the rotor rotating andprotruding from one side of the housing, wherein the rotor includes amagnet installed within the stator to rotate while interacting with thestator and a nut member coupled to the magnet, wherein a spline isprovided at an outer peripheral surface of the nut member, wherein thespline extends in an axial direction and coupled with an spline holeformed in the magnet; a bearing installed at one side of the housing; abearing cover coupled with one side of the housing, wherein the bearingcover supports the bearing; a screw member coupled with the nut memberto linearly move in a first direction and a second direction, which isopposite to the first direction, according to rotation of the rotor; anda mounting member detachably coupled to the bearing cover; wherein thebearing cover includes a coupling rim having a ring shape and coupled toone side of the housing structure, a coupling pipe extending from thecoupling rim, and a locking rim protruding radially inward from an endof the coupling pipe to make contact with an outer race of the bearing;and wherein the bearing cover comprises a coupling section protrudingradially inward from the coupling rim to make contact with the outerrace of the bearing.
 15. The step actuator as claimed in claim 14,wherein the mounting member includes a receptacle pipe installed in thecoupling pipe and a protrusion extending from the receptacle pipe in thesecond direction to support the screw member.
 16. The step actuator asclaimed in claim 14, wherein the bearing cover includes a support memberextending from an outer peripheral portion of the coupling rim in thesecond direction and a first contact member extending radially outwardfrom the support member, and the mounting member includes an extensionrim extending radially outward from an outer peripheral surface of thereceptacle pipe, a locking member extending from the extension rim inthe first direction, and a second contact member extending radiallyinward from an end of the locking member.
 17. The step actuator asclaimed in claim 16, wherein the second contact member restrainsmovement of the first contact member in the first direction.
 18. Thestep actuator as claimed in claim 16, wherein the first contact memberis formed with an embossing.
 19. The step actuator as claimed in claim16, wherein the bearing cover includes a stopper protrusion extendingradially outward from the support member, and the locking member and thestopper protrusion are arranged in a same circumferential surface. 20.The step actuator as claimed in claim 19, further comprising a lockingprotrusion extending from the extension rim in a form of a cantileverand having elasticity, wherein the locking protrusion is spaced apartfrom the locking member to restrain movement of the stopper protrusionin a circumferential direction.